Our present research is aimed at establishing the relationship between gene structure and the regulation of gene activity in eukaryotes using Dictyostelium discoideum as a developmental system. To this end, we are continuing our studies of recombinant plasmids containing short, transcribed interspersed repeat sequences which are localized at the 5' ends of mRNA. We plan on examining the transcription patterns, during development, of various single-copy genes associated with the members of the same repeat sequence family to test whether members of repeats may either be coordinately regulated or transcribed at the same level. In addition, we are trying to localize the site of initiation of transcription of these genes to determine if it may lie within the repeat. In these studies, we hope to be able to understand the function of these sequences. In a second project, we are continuing our studies of the structure and transcriptional regulation of the multi-gene family coding for actin. Specifically, we are isolating additional members of the actin gene family. These will be used to examine the comparative structure and transcription patterns of the gene family to obtain insight into the relationship between the organization of these genes and the regulation of actin protein biosynthesis during development.